712 research outputs found
Effect of Atomic Coherence on Absorption in Four-level Systems: an Analytical study
Absorption profile of a four-level ladder atomic system interacting with
three driving fields is studied perturbatively and analytical results are
presented. Numerical results where the driving field strengths are treated upto
all orders are presented. The absorption features is studied in two regimes, i)
the weak middle transition coupling, i.e.
and ii) the strong middle transition coupling
. In case i), it is shown that the ground state
absorption and the saturation characteristics of the population of level 2
reveal deviation due to the presence of upper level couplings. In particular,
the saturation curve for the population of level 2 shows a dip for . While the populations of levels 3 and 4 show a maxima when this
resonance condition is satisfied. Thus the resonance condition provides a
criterion for maximally populating the upper levels. A second order
perturbation calculation reveals the nature of this minima (maxima). In the
second case, I report two important features: a) Filtering of the Aulter-Townes
doublet in the three-peak absorption profile of the ground state, which is
achieved by detuning only the upper most coupling field, and b) control of
line-width by controlling the strength of the upper coupling fields. This
filtering technique coupled with the control of linewidth could prove to be
very useful for high resolution studies.Comment: 15 pages 12 figure
Lepton Masses in a Minimal Model with Triplet Higgs Bosons and Flavor Symmetry
Viable neutrino and charged lepton masses and mixings are obtained by
imposing a flavor symmetry in a model with a few
additional Higgs. We use two triplet Higgs which are arranged as a
doublet of , and standard model singlet Higgs which are also put as
doublets of . We break the symmetry in this minimal model by giving
vacuum expectation values (VEV) to the additional Higgs fields. Dictated by the
minimum condition for the scalar potential, we obtain certain VEV alignments
which allow us to maintain symmetry in the neutrino sector, while
breaking it maximally for the charged leptons. This helps us to simultaneously
explain the hierarchical charged lepton masses, and the neutrino masses and
mixings. In particular, we obtain maximal and zero .
We allow for a mild breaking of the symmetry for the neutrinos and
study the phenomenology. We give predictions for and the CP
violating Jarlskog invariant , as a function of the symmetry
breaking parameter. We also discuss possible collider signatures and
phenomenology associated with lepton flavor violating processes.Comment: 29 pages, 5 figures. Version to be appeared in PRD. Phenomenology of
Lepton flavor violation and possible collider signatures of this model have
been include
Non-classical photon pair generation in atomic vapours
A scheme for the generation of non-classical pairs of photons in atomic
vapours is proposed. The scheme exploits the fact that the cross correlation of
the emission of photons from the extreme transitions of a four-level cascade
system shows anti-bunching which has not been reported earlier and which is
unlike the case of the three level cascade emission which shows bunching. The
Cauchy-Schwarz inequality which is the ratio of cross-correlation to the auto
correlation function in this case is estimated to be for
controllable time delay, and is one to four orders of magnitude larger compared
to previous experiments. The choice of Doppler free geometry in addition to the
fact that at three photon resonance the excitation/deexcitation processes occur
in a very narrow frequency band, ensures cleaner signals.Comment: 18 pages, 7 figure
Spin observables and reconstruction of pi-d elastic-scattering amplitudes in transverse frame
The authors show that the measurement of only eight real parameters consisting of the differential cross section y0, the analysing power T20 and the polarisation transfer observables Cx,x, Cx,y, Cy,y, Cx,xz, Cx,yz and Cy,xz are sufficient for the complete determination of pi -d elastic scattering amplitudes in the transverse frame
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